Pressure governor



June 20, 1961 F. A. ALCARO 2,989,000

PRESSURE GOVERNOR Filed Dec. 1, 1959 3 Sheets-Sheet 1 INVENTOR.

FRANCIS A. ALCAEO A- t]; via/1 June 20, 1961 F. A. ALCARO 2,989,000

PRESSURE GOVERNOR File d Dec. 1, 1959 S Sheets-Sheet 2 June 20, 1961 F. A. ALCARO 2,989,000

PRESSURE GOVERNOR Filed Dec. 1, 1959 3 Sheets-Sheet 3 l L R FIG. 5.

FIG. 9.

IN VEN TOR.

FQA VC/S 4. ALCARO United States Patent 2,989,000 PRESSURE GOVERNOR Francis A. Alcaro, Eastchester, N.Y., assignor to Santa Fe Manufacturing 'Corp. Filed Dec. 1, 1959, Ser. No. 856,477 12 Claims. (Cl. 10316) The present invention relates generally to pumpingstation equipment and in particular to a device for automatically governing pumping pressures.

A typical pumping station installation includes a pump, an intake line delivering a pumping fluid such as oil or water to the pump at an intake pressure, a motor driving the pump to boost the pumping fluid to a higher discharge pressure, and a discharge line through which the pumping fluid is discharged at the discharge pressure. Normally it is desired that the pump be operated at a speed calculated to provided a certain selected pressure differential or boost from the intake side to the discharge side thereof. Thus, if in the course of the pumping operation the pressure differential exceeds the selected value, because of either a drop in the intake pressure or a rise in the discharge pressure, the pump is pumping too fast for the prevailing conditions and should be slowed down. If,

on the other hand, the pressure differential falls below the selected value, because of either a rise in the intake pressure or a drop in the discharge pressure, then the pump is not pumping fast enough for the Prevailing conditions and should be speeded up. For adjusting the pumping speed the motor which drives the pump is generally provided with a speed control, such as a rheostat in the case of an electric motor, or a throttle if an internal combustion engine is employed. However, to avoid the necessity for constant attention, it is desirable to provide a device which continuously measures the differential between the intake and discharge pressures and automatically adjusts the speed control to keep the differential at the selected value.

In addition, it is desirable that such a device react to certain emergency conditions which may arise independently of the pressure differential. For example, if the intake pressure falls below a selected minimum because of a disruption of the intake supply, or if the discharge pressure should rise above a selected maximum owing to a blockage of the discharge line, it would then be desirable to terminate the pumping operation. Such termination should take place immediately upon the occurrence of the emergency condition and without the necessity for any human attention. Therefore it is desirable that the device be automatic and rapid in its response. Furthermore, the device should fail safe by terminating the pumping operation under certain abnormal conditions which make the device inoperable, such as failure of certain key operating parts, or the absence of sufiicient hydraulic pressure to actuate the device properly.

Accordingly it is broadly an object of this invention to provide a device which will fulfiill one or more of the I aforesaid requirements. More specifically it is an-object of this invention to provide an automatic pressure governor which continuously measures the differential between the intake and discharge pressure of a pump and automatically adjusts the speed of the driver motor to Patented June 20, 1961 absence of sufficient hydraulic pressure in the pumping system to actuate the pressure governor.

In accordance with an illustrative embodimentof this invention which will serve to demonstrate various features and advantages as well as further objects thereof, there is provided a pressure governor device which is designed for use with a motor which has a speed control and is connected to drive a pump which receives a pumping fluid at an intake pressure and discharges the pumping fluid at a discharge pressure higher than the intake pressure. The pressure governor includes an automatic pressure differential stabilizing means, and an automatic emergency speed reduction means. There are means which connect the pressure differential stabilizing means to sense the differential between the intake pressure and the discharge pressure and which also connect the emergency speed reduction means to sense the discharge pressure and the intake pressure respectively. There are further means connecting the pressure differential stabilizing means and the emergency speed reduction means to operate the speed control of the motor. The pressure differential stabilizing means is operable in response to variation of the pressure differential from a selected value thereof to adjust the speed of the motor in the direction to restore the selected value of the pressure differential. The emergency speed reduction means, on the other hand, is operable regardless of the pressure differential, responding to the occurrence of either one of two emergency conditions, rising of the discharge pressure above a selected maximum or falling of the intake pressure below a selected minimum, to reduce the speed of the motor to a minimal level. In addition the pressure governor includes means for adjusting the response of the pressure differential stabilizing means to select the selected pressure diflerential value and means for adjusting the response of the emergency speed reduction means to select the selected maximum and the selected minimum. Further means are provided which are operable in response to reduction of the speed of the motor to a minimal level to releasably maintain the speed of the motor substantially at that level. There may also be provided additional means for manually adjusting the speed of the motor so that the motor may be restored to a normal operating speed after the aforesaid emergency conditions have been corrected, and means for maintaining the speed of an internal combustion driver motor at a warm-up level when beginning the pumping operation after the motor has lain idle for a time.

The foregoing brief description of the invention, as well as additional features and advantages inherent in the invention, may be more fully appreciated by reference to the following detailed description, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a vertical cross-section of a pressure governor in accordance with the present invention taken along the lines 11 of FIG. 3, the speed control linkage of the pressure governor being illustrated in position to hold the running speed of the driver motor at a maximum level;

FIG. 2 is a side elevational view of the warm-up holder and emergency holder means of the pressure governor of FIG. 1, illustrated in position to maintain the speed of the driver motor at a warm-up level;

FIG. 3 is a top plan view of the pressure governor of FIG. 1;

FIG. 4 is a vertical cross-section of the pressure governor of FIGS. 1 and 3 taken along the lines 44 of FIG. 3, and illustrating one embodiment of a portion of the emergency speed reduction means;

FIG. 4a is a vertical cross-section similar to FIG. 4 and illustrating an alternative embodiment of the portion of the emergency speed reduction means illustrated there- FIG. 5 is a schematic diagram illustrating three pumping stations in series, each of which includes a pump driven by a motor which in turn is controlled by -a pressure governor in accordance with this invention;

FIG. 6 is a schematic view of the speed control linkage of the pressure governor of FIGS. 1, 3 and 4 illustrated in position to releasably hold the speed of the driver motor at a minimal or idle level;

FIG. 7 is a similar schematic view of the speed control linkage of FIG. 6 illustrated in a position to maintain the speed of the driver motor at a normal running level; FIG. 8 is a similar schematic view of the speed control linkage of FIGS. 6 and 7 illustrated in the position to reduce the speed of the driver motor to a minimal level in response to the occurrence of some emergency condition; and,

FIG. 9 is a schematic diagram illustrating the captive fluid systems which connect the pressure differential stabilizing means and the emergency speed reduction means of the pressure governor of FIGS. 1, 3 and 4 to sense the various operating pressures of the pumping system.

Referring now specifically to FIG. of the drawings, there is seen a series of pumping stations, indicated generally by the numerals 20, 22 and 24, connected by a main line 26 through which a pumping fluid flows in the direction indicated by the arrows. Each of the pumping stations includes a pump 28, an internal combustion engine 30, and a pressure governor 32 in accordance with this invention. As indicated schematically by the dotted lines, each motor 30 is connected to drive a pump 28 for drawing in pumping fluid at the right at an intake pressure and ejecting the pumping fluid at the left at a discharge pressure higher than the intake pressure. The dotted lines connecting the pressure governors 32 to the driving motors 30 indicates schematically that the pressure governor 32 of each pumping station is connected to the throttle of the motor 30 of that pumping station for adjusting the speed thereof so as to govern the rate at which the pump 28 operates. In addition, there are branch lines 34 and 36 connecting the pressure governors 32 to the intake and discharge side of the pumps 28 respec- .tively, schematically illustrating that the pressure governors 32 are connected to measure these operating pressures at each of the pumping stations.

The pumping fluid which passes through the main line 26 is not itself allowed to enter the pressure governor 32, as this fluid, which might for example be crude oil Or unfiltered water, might do some damage to the pressure governor. The lines 34 and 36, as seen in FIG. 9, are connected to conduct the pumping fluid, designated 38, into a pair of housings 40 and 42 respectively within which are mounted compressible bellows 44 and 46 respectively. The pumping fluid 38 within the housings 40 and 42 tends to compress the bellows 44 and 46 in proportion to the pressure under which such fluid is introduced into the housings. The branch lines 34 and 36 are connected to the intake and discharge sides respectively of the pump 28, so that bellows 44 senses the intake pressure, while bellows 46 senses the discharge pressure. :Inside bellows 44 and 46 is a captive operating fluid 48 sufficiently refined to pass through the pressure governor 32 without causing damage thereto. Fluid 48 serves to transmit the intake and discharge pressures sensed by bellows 44 and 46 respectively through conduits 50 and 52 connected respectively thereto. The conduits 50 and 52 are connected by means of various other conduits to enable the fluid 48 to operate the pressure differential stabilizing and emergency speed reduction means of the pressure governor 32 in a manner which will subsequently be described in detail.

Turning now to the details of the pressure governor 32, and referring specifically to FIGS. 1-4 and 6-8 of the drawings, the pressure governor is mounted upon a base 60 and is partly contained within a casing 62. A connecting rod 64 is provided for engaging the speed con- --trol (not shown) of the motor 30 to adjust the speed thereof. The connecting rod 64 moves vertically, and is connected to the s eea'eomrolin such manner that downward motion of the rod 64 causes an increase, and upward motion thereof causes a decrease in the speed of motor 30. For controlling the motion of connecting rod 64 an actuating lever 66 is connected for pivotal movementthereof to move the rod 64 vertically to vary the motor speed. For guiding the pivotal movement of the actuating lever 66 there is provided a toggle linkage 68, 69 which is pivotally connected at one end to the base 60 and at the other end is pivoted to the actuating lever 66 and connecting rod 64 in such manner that the toggle linkage 68, 69 closes upon acceleration of the motor 30 and opens upon deceleration thereof, as may be seen by comparing the position of the toggle linkage 68, 69' in FIG. 1, which shows the members 64 and 66 in position to maintain the speed of motor 30 at a maximum running level, with the position of the same linkage in FIG. 2, which illustrates the members 64 and 66 in position to maintain the speed of the motor 30 at a warm-up level.

In order to maintain the speed of motor 30 at a warmup level when first starting the pumping operation after an idle interval, there is provided a warm-up holder 70 loosely pivoted at one end on a bracket 72 and formed with a crescent-shaped cut-out 70:: at the free end thereof which is sized to engage an elongated pivot pin 72 which pivotally connects links 68 and 69 to form the knee of the toggle. As seen in Fig. 2, the warm-up holder 70 may be swung outwardly toward the toggle linkage 68, 69 and braced against the elongated pivot pin 72 to hold the toggle linkage 68, 69 in a partly closed position so that the motor 30 will run at a Warm-up speed. The cut-out 70a partially encircles the elongated pivot pin 72 to prevent disengagement of the warm-up holder 70 therefrom. While the warm-up holder is braced thereagainst the pin 72 at the knee of the toggle linkage cannot move to the right, and consequently the toggle linkage cannot return to the fully extended or open position, thus preventing the speed of motor 30 from falling below the warm-up level. For manually opening and closing toggle linkage 68, 69 to set the speed of the motor 30 by hand just prior to engaging the warm-up holder 70, or at other times, there is provided a handle 74, best seen in FIG. 3, which is mounted at the end of elongated pivot pin 72.

The automatic pressure differential stabilizing means includes a double-ended differential cylinder which is mounted upon the base 60 and enclosed within the easing 62. A double-ended differential piston 82, both ends of which have the same area, is reciprocably mounted in the differential cylinder 80. Conventional sealing rings 83 are provided to make a sealing fit between the piston 82 and cylinder 80 at both ends thereof. The discharge and intake pressure sensing systems described above are connected respectively to opposed ends of the doubleended differential cylinder 80 to bias the double-ended differential piston 82 in proportion to the differential between the intake and discharge pressure. Specifically, a conduit 84 is connected between the conduit 50 and the lower end of the double-ended differential cylinder 80 to carry the captive operating fluid 48 from the bellows 44 so as to impress the intake pressure sensed by the bellows 44 upon the lower end of the double-ended differential piston 82. Similarly, a conduit 86 is connected between the conduit 52 and the upper end of doubleended differential cylinder 80 to carry the captive operating fluid 48 from the bellows 46 to impress the higher discharge pressure sensed thereby upon the upper end of the double-ended differential piston 82. As a result of the differential between the intake and discharge pressures which are exerted in opposite directions against the opposed ends of double-ended differential piston 82, a net downward biasing force is exerted on the piston 82 by the pressure sensing system. Because the opposed ends of the double-ended differential piston 82 are of equal aie'a, this net biasingforce exerted thereon by the pressure sensing system is proportional to the pressure differential, and changes as the pressure differential changes. In order that motion of the piston 82 in response to such changes in the pressure differential may be transmitted to the actuating lever 66 so that the latter is moved to adjust the speed control, actuating lever 66 extends through a slot 62a in the wall of casing 62, opposedslots 80a and 80b in the mid-section of cylinder 80, and a slot 62b in an inner partition of the casing 62, and is pivotally connected to the mid-section of piston 82 by a pivot pin 88.

'In order to compensate for the net biasing force ex- "erted on differential piston 82 by the pressure sensing systems so as to keep the differential piston 82 in equilibrium at a position between the opposed ends of double ended differential cylinder 80, there is provided a pair of differential compensating tension springs 90 and 92 which are pivotally connected at their lower ends to the actuating lever 66 on opposite sides of pivotal pin 88 to bias the piston 82, to which the actuating lever 66 is connected by pivot pin 88, in a direction opposite to the biasing force exerted thereon by the pressure sensing system. The upper ends of the differential compensating springs 90 and 92 are connected to knurled adjustment knobs 94 and 96 respectively which are threadedly mounted on the casing 62 so that they can be adjusted vertically to vary the tension of the springs 90 and 92. Ball bearing tension spring mountings of any conventional type, such as mounting 93, are employed to prevent twisting of the springs incident to the rotary adjusting motion of knobs 94 and 96. Since adjustment of the tension of the springs 90 and 92 varies the compensatory biasing force exerted thereby on the piston 82, this has the effect of changing the value of the pressure differential for which the springs 90 and 92 will hold piston 82 in equilibrium. Thus a convenient means is provided for bringing the piston 82 into an equilibrium condition at some position between the ends of the double-ended differential cylinder 80 at a selected value of the pressure differential.

Once an equilibrium condition of the piston 82 is established, the latter will be reciprocated downwardly or upwardly from its equilibrium position in response to increases and decreases respectively in the pressure differential above or below the selected equilibrium-producing value thereof. Because of the pivotal connection 88 between the piston 82 and the actuating lever 66 such reciprocation of the piston 82 serves to impart a pivotal movement to the actuating lever 66 which in turn operates connecting rod 64 to adjust the speed of the motor. The differential compensating springs 90 and 92 exert their combined upward biasing force on the piston 82 via the actuating lever 66, and the spring 90 is made stronger than spring 92 so that they exert unequal forces on the actuating lever 66 on opposite sides of pivot pin 88. Consequently there is a tendency for the actuating lever 66 to be biased for clockwise rotation about the pivot pin 88 and to assume a slanted orientation as" seen in FIGS. 1 and 7. A fulcrum roller 100 is rotatably mounted in the slot 62a and positioned to engage the downwardly slanting end of actuating lever 66 when the piston 82 is moved downwardly toward any one of a range of possible equilibrium positions between the opposed ends of doubleended differential cylinder 80, so that regardless of which equilibrium position within that range is assumed by the double-ended piston 82 at the particular selected value of the pressure differential, the fulcrum roller 100 will engage the actuating lever 66. FIGS. 1 and 8 illustrate the upper and lower limitingpositions respectively of the range of positions which the piston 82 can assume and be able to hold actuating lever 66 in contact with the fulcrum roller 100 provided the position of the toggle linkage 68, 69 at the moment is not such as to prevent contact. FIG. 7 illustrates a typical intermediate position ofthe piston 82 between the aforesaid limiting positions.

The pressure of fulcrum roller 100 against the actuating lever 66 causes pivotal movement of the actuating lever 66 about fulcrum roller 100 in response to reciprocation of the piston 82 from its equilibrium position by a variation of the pressure differential from the selected value thereof. An increase in the pressure differential above the selected value theerof causes piston 82 to be reciprocated downwardly, and this in turn causes actuating lever 66 to be pivoted counter-clockwise about fulcrum roller 100 so as to open toggle linkage 68, 69 and move connecting rod 64 upwardly to decrease the speed of motor 30 and thus to compensate for the increase of the pressure differential and restore the selected value thereof by reducing the pumping efforts of pump 28. In the event of a decrease of the pressure differential below theselected value thereof the differential compensating springs and 92 meet less opposition and are effective to reciprocate piston 82 upwardly, and, because of the greater strength of spring 90, to pivot actuating lever 66 in a clockwise direction about the fulcrum roller as the piston 82 rises as to close toggle linkage 68, 69 and move connecting rod 64 downwardly to increase the speed of motor 30, thereby augmenting the pumping efforts of pump 28 and thus compensating for the decrease in the pressure differential and restoring the selected value thereof. As the selected value is restored, after either arise thereabove or a decrease therebelow, the differential piston 82 will return to the particular equilibrium position associated with that selected value and consequently the pressure differential will tend to stabilize itself at the selected value. If a different selected value of the pressure differential is desired, it is only necessary to adjust the tension of springs 90 and 92 by means of knobs 94 and 96 so as to establish an equilibrium condition of the differential piston 82 at some other value of the differential between the intake and discharge pressures. Set screws 97 and 99 are threadedly mounted in a side wall of casing 62 to lock adjustment knobs 94 and 96 respectively in place once the desired setting thereof has been attained.

For reducing the speed of motor 30 to a minimal level in response to the occurrence of specific emergency conditions there is provided an automatic emergency speed reduction means. This includes an emergency cylinder bored into casing 62 and capped with a tightly fitting plug 111, and an emergency piston 112 reciprocably mounted in the emergency cylinder 110. The upwardly slanted end of actuating lever 66 extends to a position immediately beneath the emergency piston 1 12 and has a roller 114 rotatably mounted thereon. A push rod 116 depends from the emergency piston 112 and passes through an opening in the lower end of the emergency cylinder 110 toward the roller 114. The piston 112 includes an enlarged piston head 112a fitted with a sealing ring 113 which makes a sealing fit with cylinder 110, and a projecting nose 1 12]; of reduced diameter which extends upwardly from piston head 112a to limit the upward travel thereof to provide a clearance space between the piston head 112a and the top of cylinder 110 into which an operating fluid can be injected to reciprocate the piston 112 downwardly within the emergency cylinder 110 so that the push rod 116 drives the roller 114 against an anvil 118 mounted on the base 60 therebelow, thus pivoting the actuating lever 66 as far as possible in a counter-clockwise direction to throttle motor 30 down to idling speed. The described arrangement permits the actuating lever 66 to be pivoted in a counterclockwise direction about either the fulcrum roller 100 or the pivot pin 88 upon the occurrence of emergency conditions resulting in reciprocation of emergency piston 112. This is advantageous because if any difficulty is encountered in pivoting the actuating lever 66 counterclockwise about fulcrum roller 100 and moving piston 82 downwardly therewith owing to the resistance offered by the captive operating fluid 48 located in the lower end ofcylinder 80 below the piston82, the actuating lever can nevertheless be pivoted in a counter-clockwise direction about the pivot pin 88 without the necessity of moving piston 82 downwardly therewith so that more rapid reduction of the speed of motor is accomplished under such emergency conditions without having to wait for piston 82 to be reciprocated all the way to the lower end of cylinder 80. For holding the speed of motor 30 at a minimal level after the emergency speed reduction means has been called intooperation there is provided an emergency holder means. This includes a magnetic material mounted near the knee of toggle linkage 68, 69, such as the metal comprising the links 68 or 69 of the toggle itself or the elongated pivot pin 72, and a magnet 130 mounted upon bracket 72 in position to cooperate with the magnetic material at the knee of the toggle linkage 68, 69 for snapping the knee against the magnet 130 and pulling the toggle linkage into a slightly ovcrcenter and substantially open position as is illustrated in the schematic view. of FIG. 8. Once the toggle has been snapped against the magnet 130, it will be releasably held in the substantially open overcenter position and will thus maintain the speed of the motor 30 at a minimal level, that is at a speed only slightly higher than the speed at which the motor 30 runs when the toggle linkage 68, 69 is completely open or extended. Once it is desired to resume normal pumping operation, handle 74 is employed to manually release the magnetic material of the toggle linkage 68, 69 from the magnet 130 and to reclose the toggle linkage for accelerating the motor 30.

For actuating the emergency speed reduction mechanism there is provided a source of an operating fluid under pressure which is fed into the clearance space at the upper end of the emergency cylinder 110 to reciprocate the emergency piston 112 downwardly. There are further provided discharge and intake pressure valves which normally block the flow of the operating fluid into emergency cylinder 110 but which are operable in response to rising of the discharge pressure above a selected maximum and falling of the intake pressure below a selected minimum respectively to allow the operating fluid to flow into the emergency cylinder 110 for initiating emergency speed reduction. A conduit 140 is connected to conduit 52 to deliver captive fluid 48 supplied by the discharge pressure sensing bellows 46 to the lower end of a discharge pressure valve cylinder 142 and then upwardly through the cylinder 142 and through a further conduit 144 which is connected to cylinder 142 somewhat above conduit 140 and on into the emergency cylinder 110. The conduit 144, cylinder 142, and terminal portion of conduit 140 are formed directly in the casing 62. An additional conduit 146 is also connected to conduit 52 to conduct captive fluid 48 supplied by the discharge pressure sensing bellows 46 through an intake pressure valve guideway 148 and then through a further conduit 150 to the emergency cylinder 110. The conduit 150, guideway 148, and terminal portion of conduit 146 are also formed directly in the casing 62. Thus the operating fluid 48 is delivered under the discharge pressure to the emergency cylinder 110 along two alternative routes, one of the routes passing through the discharge pressure valve cylinder 142 and being governed by the discharge pressure valve, and the other route passing through the intake pressure valve guideway 148 and being governed by the intake pressure valve as will subsequently be explained.

The discharge pressure valve includes the discharge pressure valve cylinder 142 through which the operating fluid 48 must pass on one of the two alternate routes to the emergency cylinder 110, and a discharge pressure valve piston 160 reciprocably mounted therein. The operating fluid 48 enters through conduit 140 at the lower end of the cylinder 142 and must pass upwardly there- ,through and exit at a higher level through conduit 144.

The piston 160 includes an enlarged piston head 160a which is fitted with conventional sealing rings '161 sized to make a sealing fit-with the cylinder 142, the lower ring being positioned between conduit and conduit 144 so as to prevent passage of operating fluid 48 therebetween through cylinder 142. A stem 16% of reduced diameter depends from the piston head a to limit downward travel thereof and provide a clearance space between the piston head 160a and the lower end of cylinder 142 into which the operating fluid 48 can be injected from the conduit 140 to exert a pressure for biasing piston head 160 upwardly. A T-shaped discharge pressure valve passage 162 extends through the piston 160, and includes a horizontal bore through piston head 160a and a vertical bore extending from the horizontal bore through the lower end of stem 16%. The operating fluid 48 is prevented by -lower ring 161 from entering passage 162 except through the opening thereof at the lower end of stem 160b, but the latter opening is sealed by a sealing pad 164 formed of a compressible material and positioned on a plug 165 threaded into the lower end of cylinder 142 so that piston 160 may be pressed downwardly into sealing relationship with pad 164. The force exerted on the discharge pressure valve piston 160 by the captive fluid 48 introduced under the discharge pressure into cylinder 142 by conduit 140 tends to force the piston 160 upwardly out of sealing relationship with the sealing pad 164 to admit the fluid 48 into emergency cylinder 110 to initiate emergency speed reduction. However, a discharge pressure valve compression spring 166 is arranged with its lower end bearing against piston 160 to bias the latter downwardly into sealing relationship with the sealing pad 164, and the spring 166 is sufiiciently strong to allow movement of the piston 160 upwardly against the biasing force thereof and out of sealing relationship with the sealing pad 164 only when the discharge pressure exerted on the piston 160 by the captive fluid 48 exceeds a selected maximum determined by the magnitudeof the biasing force of spring 166. The upper end of spring 166 bears against an adjustment knob 167 which is threaded into the upper end of cylinder 142 and is vertically adjustable to vary the compression of spring 166. This in turn adjusts the magnitude of the biasing force exerted on piston 160 by spring 166 so as to select the, maximum value of the discharge pressure which must be exceeded in order to reciprocate the piston 160 and thus initiate emergency speed reduction. In order to prevent twisting of the spring 166 during adjustment of knob 168, the latter may be provided with a conventional ball bearing pressure plate similar to the ball bearing mounting 9.3 of FIG. 1 but designed for use with a compression spring instead of a tension spring. A set screw 169 is threaded in a side wall of casing 62 to lock the adjustment knob 167 in place when the desired setting thereof is attained. The view of FIG. 4 illustrates the manner in which a set screw dog 169 may be used to prevent the set screw 168 from squeezing the threads of adjustment knob 167 out of shape. The dog 169 consists of a cylindrical member small enough to slide freely in the threaded bore in which set screw 168 is mounted, and having at one end a plane surface against which the set screw 168 bears to exert its locking pressure, and at the other end a scalloped surface shaped to conform to the threads of adjustment knob 167 so as to transmit the locking pressure of set screw 168 to the adjustment knob 167 without distorting the threads of the latter. Similar set screw dogs (not shown) may be employed in conjunction with set screws 97 and 98 to protect the threads of adjustment knobs 94 and 96 respectively.

If it is found that the spring 166 puts too much thrust against the sealing pad 164, resort may be had to the alternative embodiment of a discharge pressure valve illustrated in FIG. 4a, wherein parts corresponding to those of FIG. 4 are given corresponding reference numerals distinguished by prime marks. In this embodiment the lower end of the stem 16% of piston 160' is closed off at the end but is formed with ports 170 about the circumference thereof which communicate with the passage 162' extending therethrough. The piston 160 has a tapered mid-section 1600' located between the conduit 140 and the ports 170 which rests against a compressible sealing ring 17=1 mounted in the cylinder 142' with only enough force to prevent the operating fluid 48 delivered through the conduit 140 from gaining access through the ports 170 to the passage 162' which leads via conduit 144' to the emergency cylinder. The remainder of the thrust of the discharge pressure valve spring 166 which biases piston 160' downwardly is taken by a bearing member 172 which is threadedly mounted on casing 162' for adjustment upwardly or downwardly respectively to decrease or increase the pressure against ring 171. When a satisfactory setting of the bearing member 172 is arrived at, it may be locked in place by means of a lock nut '174 which is threaded on the lower end of the member 172. A washer 176 and a secondary sealing ring 178 cooperate to prevent leakage through the threaded bore in which the member 172 is mounted. When the discharge pressure exceeds the selected maximum the piston 160' is raised against the biasing force of the spring 166 and is thereby moved out of contact with the ring 170 to permit the operating fluid 48 to pass below sealing ring 171 and pass through ports 170 to the passage 162 and then on into the emergency cylinder to initiate emergency speed reduction.

' For governing the flow of operating fluid 48 through conduit 150 into emergency cylinder 110 according to the intake pressure there is provided an intake pressure valve which includes an intake pressure valve cylinder 198 which is located immediately below the intake pressure valve guideway 148 and communicates therewith, and an intake pressure valve piston 192 reciprocably mounted in the cylinder 190. The piston 192 includes an enlarged piston head 192a fitted with a conventional sealing ring 193 which makes a sealing fit with the cylinder 190 and a depending stem 1921) which extends into a blind hole 190a at the bottom of cylinder 190. The stem 19212 is sized for a close sliding fit with the hole 190a so as to help align the piston 192 within the cylinder 190, and also has a length exceeding the depth of hole 190a so as to limit the downward travel of piston 192 and assure a clearance space between the piston head 192a and the lower end of cylinder 190. A conduit 194 is connected to the lower end of cylinder 190 to deliver into the aforesaid clearance space the captive operating fluid 48 from the intake pressure sensing bellows 44 which is effective to bias the intake pressure valve piston 192 upwardly. 'An intake pressure valve plunger 196 sized for a close sliding fit with guideway 148 is movably mounted therein, and is positioned above the piston 192 and in contact therewith so as to be held by piston 190 in a raised blocking position to prevent passage of the operating fluid 48 under the discharge pressure from conduit 146 to the aligned conduit 150 through the guideway 148. The plunger 196, however, is formed with a relieved section 196a which is shaped to define an intake pressure valve passage located above the conduits 146 and 150 so as to conduct the captive fluid 48 under the discharge pressure from conduit 146 through the guideway 148 and on into the conduit 150 to the emergency cylinder 110 to initiate emergency speed reduction only when the intake pressure valve plunger 196 is lowered from its blocking position to a conducting position in which the passageway 196a is aligned with conduits 146 and 150. The piston 192 urges the plunger 196 upwardly toward its blocking position in which the passageway 196a is above the position of alignment which enables the operating fluid 48 to pass into the emergency cylinder 110, but there is provided "an intake pressure valve compression spring 198 the lower end of which bears against plunger 196 to bias the latter downwardly toward the conducting position. The force of the spring 198, however, is sufliciently weak to move the plunger 196 downwardly into its conducting position only when the opposing upward force of the intake pres sure upon piston 192 falls below a selected minimum which depends upon the magnitude of the biasing force of spring 198. There is provided an adjustment knob 200 upon which the upper end of spring 198 bears and which is threadedly mounted in casing 62 for vertical adjustment to vary the compression of the spring 198 so as to adjust the biasing force thereofi to select the minimum value below which the intake pressure must fall in order to permit downward movement of plunger 196 under the urging of the spring 198 to initiate emergency speed reduction. The adjustment knob 200 may be provided with a set screw 202 and a set screw dog and ball bearing pressure plate of the type described above in connection with adjustment knob 167. It will be appreciated that although the intake pressure valve responds to the intake pressure as sensed by the operating fluid 48 transmitted to cylinder 19% from the intake pressure sensing bellows 44 via conduit 194, actual reciprocation of the emergency piston 112 is performed by the operating fluid 48 which is delivered under the higher discharge pressure from the discharge pressure sensing bellows through conduits 146 and 150 to the emergency cylinder 110. In this way the greater operating force of the discharge pressure is employed to do the work, but the intake pressure is utilized as a control relay which triggers the operation.

Thus, upon the occurrence of either of the emergency conditions, the operating fluid 48 under the discharge pressure will be introduced into the emergency cylinder 1 10 to force the emergency piston 112 downwardly and cause the push rod 116 to rotate the actuating lever 66 counterclockwise for reducing the speed of the motor 30 to a minimal level. Subsequently, when it is desired to restore the speed of motor 30' to its normal operating level, difficulty may be encountered in bringing the emergency piston 112 back-up to its normal operating position to permit the actuating lever 66 be rotated clockwise for restoring the speed control to its normal position. The difliculty arises when the upper part of emergency cylinder 1'10 remains filled with the captive operating fluid 48. For such contingencies there is provided a hand pump 210, illustrated schematically in FIG. 9, which is connected to the emergency cylinder by means of a conduit 212, the terminal portion of which is formed directly in the casing 62, and the conduit 150. The hand pump 210 is used to draw the captive operating fluid 48 through the conduits and 212 out of the emergency cylinder 110 so that the emergency piston 112 can be moved upwardly to its normal operating position when the actuating lever 66 is rotated in the clockwise direction to restore the speed of motor 30 to its normal operating level. A conduit 214 is connected to the discharge side of the hand pump 210 and serves to deliver the operating fluid 48 pumped from the emergency cylinder 110 to the conduit 52 so that it is reintroduced into the discharge pressure sensing system.

In the event of leakage of the captive operating fluid 48 from either the intake or discharge pressure sensing systems a reservoir 220 containing a supply of the captive operating fluid 48 feeds the latter by gravity through a conduit 22 controlled by a main shut-off valve 224 and then through either a further conduit 226 controlled by a check valve 228 to restore fluid to the discharge pressure sensing system or to an alternative further conduit 230 controlled by a check valve 232 to restore the captive operating fluid 48 to the intake pressure sensing system. Whenever in the course of operation of the pressure governor 32 it is thought that the level of the captive operating fluid 48 within the intake and discharge pressure sensing systems has fallen too low, the operator need only open the main shut-off valve 224, at which time the intake and discharge pressure sensing systems will automatically draw as much of the gravity fed captive fluid 48 greases 1.1 from the reservoir 220 as is required to replenish their supply thereof. The check valves 228 and 232 serve'to assure that fluid can only be drawn from the reservoir 220 into the pressure sensing systems and will not be forced by a back pressure back into, the reservoir 220.

In order to facilitate the fullest understanding of this invention there will now be described a cycle of operation of the pressure governor 32 under various operating conditions, both typical and atypical, which might occur. Before the start of the pumping operation there will be no pressure on the discharge side of the pump 28, and so no fluid will be introduced to the upper end of the differential cylinder 80 to force the differential piston 82 downwardly. Consequently the upward biasing force of the differential compensating springs 90 and 92 will be unopposed, and the actuating linkage of the pressure goverhor 32 will be in the posit-ion indicated schematically in FIG. 6. That is, the operating lever 66 will be raised upwardly, with the roller 114 contacting the push rod 116 at the left and the toggle linkage 68, 69 opened to a slightly overcenter position. The toggle linkage 68, 69 will be held in that position by the magnet 13!). The first step in initiating the pumping operation is the starting of the internal combustion engine 30. Once this is accomplished it will normally be desired to warm up the motor 38 for a short time before bringing it up to normal operating speed. This may be done by grasping the manual operating handle 74 and moving it to the left to release the toggle linkage 68, 69 from the magnet 130 and to partially close the toggle linkage 68, 69 for bringing the speed of motor 30 up to a somewhat higher warmup level. Then the warm-up holder 70 is pivoted toward the toggle linkage 68, 69 and the cut-out 70a is braced against the elongated pivot pin 72 at the knee of the toggle to hold the knee to the left and keep the toggle in a flexed or closed position as indicated in FIG. 2 so that the motor 30 will continue to run at the aforesaid warm-up speed. As the running of the motor 30 causes the pump 28 to build-up the pressure on the discharge side thereof, the operating fluid 48 introduced at the upper end of the cylinder 80 will drive the piston 82 and actuating lever 66 downwardly against the biasing force of the springs 90 and 92, until a point is reached at which the toggle linkage 68, 69 is flexed or closed sufficiently to move the knee thereof to the left and disengage the elongated pivot pin 72 from the cut-out 70a. The warmup holder 70 will then fall from its operating position fund be automatically returned to the position indicated in FIG. 1 so that it no longer restrains the toggle linkage 68, 69. As the piston 82 continues to move downwardly a point is reached at which the actuating lever 66 first makes contact with the fulcrum roller 12%, as illustrated in FIG. l. At this point the toggle linkage 68, 69 is flexed to a considerably greater extent than in the warmup position indicated in FIG. 2, and the motor 30 is accordingly running at a high speed. Further build-up of the discharge pressure causes the piston 82 to be reciprocated further downwardly from the position illustrated in FIG. 1, which causes the actuating lever 66 to be pivoted counterclockwise about the fulcrum roller 100 so as to decrease the speed of motor 30 by opening the toggle linkage 68, 69 from the position of maximum closure illustrated in FIG. 1. Eventually an equilibrium position of the piston 82 will be reached when the discharge pressure biasing it downwardly is balanced by the intake pressure biasing it upwardly plus the upward biasing force of the springs 98 and 92. In a typical equilibrium condition such as is illustrated schematically in FIG. 7 the motor 30 runs at a normal speed, with the toggle linkage 68, 69 flexed somewhat less than in FIG. 1 but more than in FIG. 2, and the actuating lever 66 continues to contact the fulcrum roller 100 which thus serves to cause counter-clockwise rotation of the actuating lever T66 thereabout in response to downward movement of the piston 82 from its equilibrium position caused by an increase in the pressure differential to slow the motorand thus compensate for the increase. On the other hand, if the piston 82 is moved upwardly from its equilibrium position then the greater strength of spring 90 will serve to pivot the actuating lever 66 clockwise about the pivot pin 88 against the weaker tension of spring 92 to keep the actuating lever pressed against the fulcrum roller 10,0 and to cause a closure of the toggle linkage 68, which increases the speed of motor 30 and compensates for the decrease. In the equilibrium position illustrated in FIG. 7 the left-hand end of the actuating lever 66 floats freely between the push-rod1116 and the anvil 118 so that neither of these elements restricts its motion within the normal operating range. Similarly, the piston 82 in its equilibrium position floats freely under the influence of the fluid pressure biasing it at either end of the cylinder so that its freedom of movement is not restricted. Thus the actuating linkage of the differential control linkage moves freely through its operating range under the influence of variations in the pressure differential, always moving in the proper direction to compensate for such variations so that the pressure differential has a tendency to stabilize itself at a selected value dependent upon the tension of springs and 92.

If, regardless of what the differential between the discharge and intake pressures may be at the moment, the absolute value of the discharge pressure should rise above the'selected maximum, the piston would be biased upwardly by the force of the operating fluid 48 exerted on piston head 160a strongly enough to overcome the downward urging of the spring 166 and thus raise the lower end of stem 160b to allow the operating fluid 48 to pass through the passageway 162 and on through the conduit 144 into the clearance space at the upper end of emergency cylinder 110. In the alternative embodiment of FIG. 4a, the operation of the device would be similar, the modified discharge pressure valve piston 160 being raised upwardly from the seat 170 to allow the operating fluid 48 to pass the sealing ring 171 and enter the ports 170. leading to the passage 162 and then through the couduit 144' into the emergency cylinder.

Upon the falling of the intake pressure below the selectedminimum, regardless of what the differential relative to the discharge pressure may be, the upward biasing force of the operating fluid 48 under the intake pressure upon the head 192a of the piston 192 would become too weakto hold the plunger 196 upwardly in its blocking position against the downward biasing force of the spring 198, andthe plunger 196 would then be moved downwardly until the passageway 196a became aligned with the conduits 146 and 150 to allow the operating fluid 48 under the discharge pressure to enter the emergency cylinder 110.

Entrance of the operating fluid 48 under the discharge pressure into the emergency cylinder 110 under either of the emergency conditions will cause the emergency piston 112 to be reciprocated downwardly, whereupon the pushrod 116 exerts a downward force upon the roller 114, rotating the actuating lever 66 in a counter-clockwise dimotion to open the toggle linkage 68, 69 completely and thus reduce the speed of motor 30 to a minimal or idling level. The force of the push-rod 116 against the roller 114 serves to pivot the actuating lever 66 about the fulcrum roller 100, which causes the differential piston 82 to be reciprocated downwardly as the actuating lever 66 is rotated, and, if the differential piston 82 does not move downwardly promptly, the actuating lever 66 is also pivoted about pivot pin 88 to achieve the same result. Thus, the actuating lever 66 is pivoted counter-clockwise very rapidly to cut the speed of the motor 30 upon the occurrence of either of the emergency conditions, and the viscous resistance of the operating fluid 48 in the lower end of cylinder 80 would not materially slow the reaction of the pressure governor 32th'ereto. FIG. 8 illustrates schematically the condition of the pressure governor 32 upon the occurrence of an emergency condition whichca'uses aaeoo 13 a downward motion of the push-rod 116. It is seen that the roller 114 is forced down until it contacts the anvil 118, the piston 82 is forced to the lower end of cylinder 80, and the actuating lever 66 is rotated in the counterclockwise direction about fulcrum roller 100.

-It will also be appreciated from an inspection of FIG. 8 that upon the occurrence of this sort of emergency condition the toggle linkage 68, 69 is first opened completely and is subsequently snapped by the magnet 130 to a slight- 1y overcenter but substantially open position so that subsequent elforts to rotate the actuating lever 66 in a clockwise direction will not be effective to close the toggle linkage .or restore the speed of the motor 30 to an operating level. Any attempt to.produce clockwise rotation of the actuating lever. 66 would only serve to jam the knee of the toggle linkage 68, 69 against the magnet E130 because of the overcenter condition of the toggle linkage 68, 69. It will be necessary in order to enable subsequent resumption of the pumping operation for an operator to deliberately reclose the toggle linkage 68, 69 by means of the handle 74. It will be appreciated that this is a significant safety feature which allows resumption of the pumping operation after the occurrence of emergency condition only at the discretion of an operator who has decided that subsequent conditions warrant such resumption.

' It will also be appreciated from the schematic diagram of FIG. 8 that in the event that one or both of the differential compensating springs 90 and 92 should break during operation of the pressure governor 32 under nonemergency conditions the device would fail safe because the margin by which the discharge pressure exerted downwardly upon the upper end of the differential piston 82 exceeds the intake pressure exerted upwardly upon the lower end thereof would no longer be fully compensated for by the differential compensating springs 90 and 92. The equilibrium condition of piston 82 would therefore be destroyed and the piston 82'would then be reciprocated downwardly within the cylinder 80 to rotate the actuating lever 66 counter-clockwise about the fulcrum roller 100 and thus reduce the speed of the motor 30 to a minimal level and engage the emergency holder mechanism to maintain that level. Thus, it is apparent that upon the breakage of one or both of the differential compensating springs 90 and 92 the pressure governor 32 will go through an operation very similar to the emergency speed reduction operation which is initiated by the emergency piston 112 in response to pressure conditions as described above. However, in the event of *suchbreakage the response is initiated by the failure without regard to the particular levels of the various critical fluid operating pressures which normally govern such operation.

*1 On the other hand, should the differential compensat- -ing' springs 90 and 92 be in good working order but a serious leak should develop in the captive operating fluid system, then there would be insufficient downward pressure atthe upper end of the cylinder 80 to hold the piston "82 in its equilibrium position against the upward biasing force of the dilferential compensating springs 90 and 192. Thus in the event of failure of suflicient hydraulic pressure in the captive operating fluid system to operate the pressure governor 32 properly, the differential com.- lpensati ng springs 90 and 92 would pull the actuating lever 66 and dilferential piston 82 upwardly into the original 'starting position indicated schematically in FIG. 6. This 'operation would also serve to open the toggle linkage 68, 69 completely and thus to snap it into the overcenter position inwhich it is releasably held by the magnet 130.

, Thusfailure of either the differential compensating condition which produced the termination and deliberately causes a resumption thereof.

whichmay be installed in one or more pumping stations to provide precise and continuous automatic control of the differential between the pressure at the intake and discharge sides of the pump. The device is also effec tive to automatically and immediately discontinue the pumping operation upon the occurrence of certain emergency conditions along'the pumping line, such as the falling of the intake pressure below a selected minimum or the rising of the discharge pressure above the selected maximum, regardless of whether the differential between the intake and discharge pressure is or is not maintained. The device further disrupts the pumping operation if there should occur a failure within its own operating mechanism which renders it incapable of responding properly to perform the operations for which it is primarily designed. Once the pumping operation has been terminated, the pressure governor of this invention will not allow resumption thereof until an operator deliberately resets the device with the express intention of allowing the pumping operations to be resumed after determining that such action is warranted.

The particulars of the foregoing description are provided merely for purposes of illustration and are subject to a considerable latitude of modification without departing from the novel teachings disclosed herein. Accordingly, the scope of this invention is intended to be limited only as defined in the appended claims, which should be accorded a breadth of interpretation consistent with this specification.

What I claim is:

. 1. For use with a motor having a speed control and connected to drive a pump receiving a pumping fluid at an. intake. pressure and discharging said pumping fluid at a discharge pressure higher than said intake pressure, a pressure governor comprising actuating means connected to said speed control to adjust the speed of said motor, automatic pressure diflerential stabilizing means including differential cylinder means, differential piston means reciprocably mounted in said diiferential cylinder means, discharge and intake pressure sensing systems, means connecting said discharge and intake pressure sensing, systems to bias said differential piston means in proportion to the differential between said intake and discharge pressures, dilferential compensating means biasing said differential piston means in a direction opposite to the biasing force exerted by said pressure difierential for maintaining said differential piston means in equilibrium at a selected value of said pressure dilferential, said differential piston means being reciprocated in response to variations in said pressure differential from said selected value, means for operating said actuating means in response to reciprocation of said differential piston means by variations in said pressure differential from said selected value to adjust the speed of said motor in the direction to restore said selected value, means for adjusting the biasing force of said differential compensating means to select said selected value, automatic emergency speed reduction means including an emergency cylinder, means providing a source of an operating fluid and connected to deliver said operating fluid to said emergency cylinder along a pair of alternative routes, discharge pressure valve means connected to control the flow of operating fluid to said emergency cylinder along one of said alternative routes and operatively connected to said discharge pressure sensing system and operable in response to rising of said discharge pressure above a selected maximum to admit said operating fluid into said emergency cylinder, intake pressure valve means connected to control the flow of said operating fluid to said emergency cylinder along the other of said alternative routes and operatively connected to said intake pressure sensing system andoperable in response to falling of said intake pressure .below a selected minimum to admit said operating fluid into said emergency cylinder, an emergency piston mounted in said emergency-cylinder for reciprocation in response'to entrance of" saidoperatingflfluid th'ereinto, means for operating said actuating means to reduce the speed of said motor to a'minimaldevel'in response to reciprocation of said emergency piston, and means for individually adjusting the-response of said discharge pressure and intake pressure valve means to select said selected maximum and said selected minimum.

' 2. For use with a motor having a speed control and connected to drive a pump receiving a pumping fluid'at an intake pressure and discharging said pumping fluid at a discharge pressure higher than said intake pressure, a pressure governor comprising actuating means connected to said speed control to adjust the speed of. said motor, automatic pressure differential stabilizing means including differential cylinder means, differential piston means reciprocably mounted in said differential cylinder means, discharge and intake pressure sensing systems, means connecting said discharge and intake pressure sensingsystems to bias said differential piston means in proportion to the differential between said intake and discharge pressures, differential compensating means biasing said differential piston means in a direction opposite to the biasing force exerted by said pressure differential for maintaining said differential piston means in equilibrium at a selected value of said pressure differential, said differential piston means being reciprocated in response to variations in said pres- Sure differential from said selected value, means for operating said actuating means in response to reciprocation of said differential piston means by variations in said pressure differential from said selected value to' adjust the speed of said motor in the direction to restore said selected value, means for adjusting the biasing force of said differential compensating means to select .said selected value, automatic emergency speed reduction means including an emergency cylinder, means providing a source of an operating fluid and connected to deliver said operating fluid to said emergency cylinder along a pair of alternative routes, discharge pressure valve means connected to control the flow of operating fluid to said emergency cylinder along one of said alternative routes and operatively connected to said discharge pressure sensing system and operable in response to rising of said discharge pressure above a selected maximum to admit said operat ing fluid into said emergency cylinder, intake pressure valve means connected to control the flow of said operating fluid to said emergency cylinder along the other of said alternative routes and operatively connected to said intake pressure sensing system and operable in response to falling of said intake pressure below a selected minimum to admit said operating fluid into said emergency cylinder, an emergency piston reciprocably mounted in said emergency cylinder for reciprocation in response to entrance of said operating fluid thereinto, means for operating said actuating means to reduce the speed of said motor to a minimal level in response to reciprocation of said emergency piston, means for individually adjusting the response of said discharge pressure and intake pressure valve means to select said selected maximum and said selected minimum, and emergency holder means operable in response to movement of said actuating means into a position to reduce the speed of said motor to said minimal level for releasably holding said actuating means substantially in said position. v

3. For use with a motor having a speed control and connected to drive a pump receiving a pumping fluid at an intake pressure and discharging said pumping fluid at a discharge pressure higher than said intake pressure, a pres- ;suregovernorcomprising actuating means connected to said speed control to adjust the speed of said motor, automatic pressure differential stabilizing means including differential cylinder means, differential piston means reciprocably mounted in said differential cylinder means,

discharge and intake pressure sensing systemsfmeansconmeeting said discharge and intake pressure sensing systems to bias said differential piston means in proportion to' the differential between saidlintake and discharge pressures, differential compensating means biasing said differential piston means in a direction'opposite to the biasing force exerted by said pressure'differential for maintaining said differential piston means in'equilibrium at a selected value of said pressure differential, said differential piston means being reciprocated in response to variations in said pressure differential from said selected value, means for operating said actuating means in response to reciprocation of said differential piston means by variations in said pressure differential from said selected value to adjust the speed of said motor in the direction to restore said selected value, means for adjusting the biasing force of said differential compensating means to select said selected value, automatic emergency speed reduction means including an emergency cylinder, means providing a source of an operating fluid and connected to deliver said operating fluid to said emergency cylinder along a pair of alternative routes, discharge pressure valve means connected to control the flow of operating fluid to said emergency cylinder along one of said alternative routes and operatively connected to said discharge pressure sensing system and operable in response to rising of said discharge pressure above a selected maximum to admit said operating fluid into said emergency cylinder, intake pressure valve means connected to control the flow of said operating fluid to said emergency cylinder along the other of said alternative routes and operatively connected to said intake pressure sensing system and operable in response to falling of said intake pressure below a selected minimum to admit said operating fluid into said emergency cylinder, an emergency piston reciprocably mounted in said emergency cylinder for reciprocation in response to entrance of said operating fluid thereinto, means for operating said actuating means to reduce the speed of said motor to a minimal level in response to reciprocation of said emergency piston, means for individually adjusting the response of said discharge pressure and intake pressure valve means to select said selected maximum and said selected minimum, emergency holder means operable in response to movement of said actuating means into a position to reduce the speed of said motor to said minimal level for releasably holding said actuating means substantially in said position, and means for manually altering the position of said actuating means to adjust the speed of said motor.

4. For use with a motor having a speed control and connected to drive a pump receiving a pumping fluid at an intake pressure and discharging said pumping fluid at a discharge pressure higher than said intake pressure, a pressure governor comprising actuating means connected to said speed control to adjust the speed of said motor, automatic pressure differential stabilizing means including differential cylinder means, differential piston means reciprocably mounted in said differential cylinder means, discharge and intake pressure sensing systems, means connecting said discharge and intake pressure sensing systems to bias said differential piston means in proportion to the differential between said intake and discharge pressures, differential compensating means biasing said differential piston means in a direction opposite to the biasing force exerted by said pressure differential for maintaining said differential piston means in equilibrium at a selected value of said pressure differential, said differential piston means being reciprocated in response to variations in said pressure differential from said selected value, means for operating said actuating means in response to-reciprocation of said differential piston means by variations in said pressure differential from said selected value to adjust the speed of said motor in the direction to restore said selected value, means for adjusting the biasing force of. said differential compensating means to select said selected value, automatic emergency speed reduction means including an emergency cylinder, means providing a source of an operating fluid and connected to deliver said operating fluid to said emergency cylinder along a pair of alternative routes, discharge pressure valve means connected to control the flow of operating fluid to said emergency cylinder along one of said alternative routes and operatively connected to said discharge pressure sensing system and operable in response to rising of said discharge pressure above a selected maximum to admit said operating fluid into said emergency cylinder, intake pressure valve means connected to control the flow of said operating fluid to said emergency cylinder along the other of said alternative routes and operatively connected .to said intake pressure sensing system and operable in response to falling of said intake pressure below a selected minimum to admit said operating fluid into said emergency cylinder, an emergency piston mounted in said emergency cylinder for reciprocation in response to entrance of said operating fluid thereinto, means for operating said actuating means to reduce the speed of said motor to a minimal level in response to reciprocation of said emergency piston, means for individually adjusting the response of said discharge pressure and intake pressure valve means to select said selected maximum and said selected minimum, emergency holder means operable in response to movement of said actuating means into a position to reduce the speed of said motor to said minimal level for releasably holding said actuating means substantially in said position, means for manually altering the position of said actuating means to adjust the speed of said motor, and warm-up holder means for holding said actuating means in a position to maintain the speed of said motor at a warm-up level.

5. For use with a motor having a speed control and connected to drive a pump receiving a pumping fluid at an intake pressure and discharging said pumping fluid at a discharge pressure higher than said intake pressure, a pressure governor comprising an actuating lever, connecting means engaging said speed control and arranged to adjust the speed of said motor in response to pivotal movement of said actuating lever, automatic pressure differential stabilizing means including a double-ended cylinder, a double-ended piston reciprocably mounted in said double-ended cylinder, discharge and intake pressure sensing systems adatped to contain a captive fluid and including a pair of bellows positioned to sense said intake and discharge pressures respectively and conduit means connected to said bellows to transmit, said captive fluid under the pressures sensed by said bellows, said conduit means being connected to transmit said captive fluid under said intake and discharge pressures respectively to opposed ends of said double-ended cylinder to bias said doubleended piston in proportion to the differential between said intake and discharge pressures, differential compensating spring means connected to bias said double-ended piston in a direction opposite to the biasing force exerted by said pressure differential for maintaining said double-ended piston in equilibrium at a position between the opposed ends of said double-ended cylinder at a selected value of said pressure diflerentia'l, said differential piston being reciprocated from said equilibrium position toward either end of said double-ended cylinder in response to increases and decreases respectively in said pressure differential from said selected value, pivot means pivotally connecting said double-ended piston to said actuating lever, a fulcrum positioned to engage said actuating lever when said double-ended piston is in any one of a range of equilibrium positions for causing pivotal movement of said actuating lever about said fulcrum in the direction to decelerate said motor when said double-ended piston is reciprocated from an equilibrium position in said range in response to an increase in said pressure differential, said differential compensating spring means being connected to pivot said actuating lever about said pivot means and about said fulcrum in the direction to accelerate said motor when said double-ended piston is reciprocated from an equilibrium position in said range by a decrease in said pressure diflerential, automatic emergency speed reduction means including an emergency cylinder, an emergency piston reciprocably mounted in said emergency cylinder, means arranged to pivot said actuating lever about said pivot means and about said fulcrum in the direction to decelerate said motor sufliciently far to reduce the speed of said motor to a minimal level in response to reciprocation of said emergency piston, a discharge pressure valve cylinder, an intake pressure valve guideway, said conduit means being connected to deliver said cap tive fluid from said discharge pressure sensing system along alternative routes through said discharge pressure valve cylinder to said emergency cylinder and through said intake pressure valve guideway to said emergency cylinder to reciprocate said emergency piston, a discharge pressure valve piston reciprocably mounted in said discharge pressure valve cylinder arranged to block passage of said captive fluid through said discharge pressure valve cylinder and formed with a discharge pressure valve passage for conducting said captive fluid through said discharge pressure valve cylinder, sealing means positioned to seal oii said discharge pressure valve when said discharge pressure valve piston is in sealing relationship therewith, said discharge pressure valve piston being arranged to be urged out of sealing relationship with said sealing means in response to the discharge pressure exerted thereon by said captive fluid, discharge pressure valve spring means arranged to bias said discharge pressure valve piston into sealing relationship with said sealing means with suflicient force to allow movement of said discharge pressure valve piston out of sealing relationship with said sealing means only when said discharge pressure exceeds a selected maximum, an intake pressure valve cylinder, an intake pressure valve piston reciprocably mounted in said intake pressure valve cylinder, an intake pressure valve plunger movably mounted in said intake pressure valve guideway normally arranged in a blocking position to prevent passage of said captive fluid therethrough and shaped to define an intake pressure valve passage located to conduct said captive fluid through said intake pressure valve guideway when said intake pressure valve plunger is moved from said blocking position to a conducting position, said intake pressure valve piston being connected to urge said intake pressure valve plunger toward said blocking position, said conduit means being connected to deliver said captive fluid from said intake pressure sensing system to said intake pressure valve cylinder for urging said intake pressure valve piston in a direction to maintain said intake pressure valve plunger in said blocking position, and intake pressure valve spring means arranged to bias said intake pressure valve plunger toward said conducting position with a force sufficiently weak to move said intake pressure valve plunger into said conducting position only when said intake pressure falls below a selected minimum.

6. For use with a motor having a speed control and connected to drive a pump receiving a pumping fluid at an intake pressure and discharging said pumping fluid at a discharge pressure higher than said intake pressure, a pressure governor comprising an actuating level, connecting means engaging said speed control and arranged to adjust the speed of said motor in response to pivotal movement of said actuating lever, automatic pressure diiferential stabilizing means including a double-ended cylinder, a double-ended piston reciprocably mounted in said double-ended cylinder, discharge and intake pressure sensing systems adapted to contain a captive fluid and including a pair of bellows positioned to sense said intake and discharge pressures respectively and conduit means connected to said bellows to transmit said captive fluid under the pressures sensed by said bellows, said conduit means being connected to transmit said cap- 19 tive fluid under said intake and discharge pressures respectively to opposed ends of said double-ended cylinder to bias said double-ended piston in proportion to the d fferential between said intake and discharge pressures, differential compensating spring means connected to bias said double-ended piston in a direction opposite to the blasing force exerted by said pressure differential for maintaining said double-ended piston in equilibrium at a position between the opposed ends of said doubleended cylinder at a selected value of said pressure differential, said differential piston being reciprocated from said equilibrium position toward either end of said doubleended cylinder in response to increases and decreases respectively in said pressure differential from said selected value. pivot means pivotally connecting said double-ended piston to said actuating lever, a fulcrum positioned to engage said actuating lever when said double-ended piston is in any one of a range of equilibrium positions for causing pivotal movement of said actuating lever about said fulcrum in the direction to decelerate said motor when said double-ended piston is reciprocated from an equilibrium position in said range in response to an increase in said pressure differential, said differential compensatmg spring means being connected to pivot said actuating lever about said pivot means and about said fulcrum in the direction to accelerate said motor when said double-ended piston is reciprocated from an equilibrium position in said range by a decrease in said pressure differential, screw means for adjusting the biasing force exerted on said double-ended piston by said diflerential compensating spring means to select said selected pressure differential value, automatic emergency speed reduction means including an emergency cylinder, an emergency piston reciprocably mounted in said emergency cylinder, means arranged to pivot said actuating lever about said pivot means and about said fulcrum in the direction to decelerate said motor sufficiently far to reduce the speed of said motor to a minimal level in response to reciprocation of said emergency piston, a discharge pressure valve cylinder, an intake pressure valve gu deway, said conduit means being connected to deliver sald captive fluid from said discharge pressure sensing system along alternative routes through said discharge pressure valve cylinder to said emergency cylinder and through said intake pressure valve guideway to said emergency cylinder to reciprocate said emergency piston, a discharge pressure valve piston reciprocably mounted .in said discharge pressure valve cylinder arranged to block passage of said captive fluid through said discharge pressure valve cylinder and formed with a discharge pressure valve passage for conducting said captive fluid through said discharge pressure valve cylinder, sealing means positioned to seal off said discharge pressure valve passage when said discharge pressure valve piston is in sealing relationship therewith, said discharge pressure valve piston being arranged to be urged out of sealing relationship with said sealing means in response to the discharge pressure exerted thereon by said captive fluid, discharge pressure valve spring means arranged to bias said discharge pressure valve piston into sealing relationship with said sealing means with sufficient force to allow movement of said discharge pressure valve piston out of sealing relationship with said sealing means only when said discharge pressure exceeds a selected maximum, screw means for adjusting the biasing force of said discharge pressure valve spring means to select said selected maximum, an intake pressure valve cylinder, an intake pressure valve piston reciprocably mounted in said invtake pressure valve cylinder, an intake pressure valve plunger movably mounted in said intake pressure valve guideway normally arranged in a blocking position to prevent passage of said captive fluid therethrough and shaped to define an intake pressure valve passage located to conduct said captive fluid through said intake pressure valve guideway when said intake pressure valve v 20 plunger is moved from said blocking position to a conducting position, said intake pressure valve piston being connected to urge said intake pressure valve plunger toward said blocking position, said conduit means being connected to deliver said captive fluid from said intake pressure sensing system to said intake pressure valve cylinder for urging said intake pressure valve piston in a direction to maintain said intake pressure valve plunger in said blocking position, intake pressure valve spring means arranged to bias said intake pressure valve plunger toward said conducting position with a force suflicient- 1y weak to move said intake pressure valve plunger into said conducting position only when said intake pressure falls below a selected minimum, and screw means for adjusting the biasing force of said intake pressure valve spring means to select said selected minimum.

7. For use with a motor having a speed control and connected to drive a pump receiving a pumping fluid at an intake pressure and discharging said pumping fluid at a discharge pressure higher than said intake pressure, a pressure governor comprising an actuating lever, connecting means engaging said speed control and arranged to adjust the speed of said motor in response to pivotal movement of said actuating lever, a toggle linkage connected to said actuating lever to close upon acceleration and open upon deceleration of said motor, automatic pressure differential stabilizing means including a double-ended cylinder, a double-ended piston reciprocably mounted in said double-ended cylinder, discharge and intake pressure sensing systems adapted to contain a captive fluid and including a pair of bellows positioned to sense said intake and discharge pressures respectively and conduit means connected to said bellows to transmit said captive fluid under the pressures sensed by said bellows, said conduit means being connected to transmit said captive fluid under said intake and discharge pressures respectively to opposed ends of said double-ended cylinder to bias said doubleended piston in proportion to the differential between said intake and discharge pressures, differential compensating spring means connected to bias said double-ended piston in a direction opposite to the biasing force exerted by said pressure differential for maintaining said doubleended piston in equilibrium at a position between the opposed ends of said double-ended cylinder at a selected value of said pressure differential, said differential piston being reciprocated from said equilibrium position toward either end of said double-ended cylinder in response to increases and decreases respectively in said pressure differ- .ential from said selected value, pivot means pivotally connecting said double-ended piston to said actuating lever, a fulcrum positioned to engage said actuating lever when said double-ended piston is in any one of a range of equilibrium positions for causing pivotal movement of said actuating lever about said fulcrum in the direction to decelerate said motor when said double-ended piston is reciprocated from an equilibrium position in said range in response to an increase in said pressure differential, said differential compensating spring means being connected to pivot said actuating lever about said pivot means and about said fulcrum in the direction to accelerate said motor when said double-ended piston is reciprocated from an equilibrium position in said range by a decrease in said pressure differential, screw means for adjusting the biasing force exerted on said double-ended piston by said differential compensating spring means to select said selected pressure differential value, automatic emergency speed reduction means including an emergency cylinder, an emergency piston reciprocably mounted in said emergency cylinder, means arranged to pivot said actuating lever about said pivot means and about said fulcrum in the direction to decelerate said motor sufliciently far to open said toggle linkage completely for reducing the speed of said motor to a minimal level in response to reciprocation of said emergencypiston, emergency holder means including a magnetic material mounted on said toggle and a magnet positioned to cooperate therewith for snapping said toggle linkage into a substantially open'o'vercenter position and for releasably holding said toggle linkage in said overcenter position for maintaining the speed of said motor substantially at said minimal level in response to complete opening of said toggle linkage, a discharge pressure valve cylinder, an intake pressure valve guideway, said conduit means being connected to deliver said captive fluid from said discharge pressure sensing system along alternative routes through said discharge pressure valve cylinder to said emergency cylinder and through said intake pressure valve guideway to said emergency cylinder to reciprocate said emergency piston, a discharge pressure valve piston reciprocably mounted in said discharge pressure valve cylinder arranged to block passage of said captive fluid through said discharge pressure valve cylinder and formed with a discharge pressure valve passage for conducting said captive fluid through said discharge pressure valve cylinder, sealing means positioned to seal off said discharge pressure valve passage when said discharge pressure valve piston is in sealing relationship therewith, said discharge pressure valve piston being arranged to be urged out of sealing relationship with said sealing means in response to the discharge pressure exerted thereon by said captive fluid, discharge pressure valve spring means arranged to bias said discharge pressure valve piston into sealing relationship with said sealing means with suiiicient force to allow movement of said discharge pressure valve piston out of sealing relationship with said sealing means only when said discharge pressure exceeds a selected maximum, screw means for adjusting the biasing force of said discharge pressure valve spring means to select said selected maximum, an intake pressure valve cylinder, an intake pressure valve piston reciprocably mounted in said intake pressure valve cylinder, an intake pressure valve plunger movably mounted in said intake pressure valve guideway normally arranged in a blocking position to prevent passage of said captive fluid therethrough and shaped to define an intake pressure valve passage located to conduct said captive fluid through said intake pressure valve guideway when said intake pressure valve plunger is moved from said blocking position to a conducting position, said intake pressure valve piston being connected to urge said intake pressure valve plunger toward said blocking position, said conduit means being connected to deliver said captive fluid from said intake pressure sensing system to said intake pressure valve cylinder for urging said intake pressure valve piston in a direction to maintain said intake pressure valve plunger in said blocking position, intake pressure valve spring means arranged to bias said intake pressure valve plunger toward said conducting position with a force sufiiciently Weak to move said intake pressure valve plunger into said conducting position only when said in take pressure falls below a selected minimum, and screw means for adjusting the biasing force of said intake pressure valve spring means to select said selected minimum.

8. For use with a motor having a speed control and connected to drive a pump receiving a pumping fluid at an intake pressure and discharging said pumping fluid at a discharge pressure higher than said intake pressure, a pressure governor comprising an actuating lever, connecting means engaging said speed control and arranged to adjust the speed of said motor in response to pivotal movement of said actuating lever, a toggle linkage connected to said actuating lever to close upon acceleration and open upon deceleration of said motor, a handle on said toggle linkake for manually opening and closing said toggle linkage to adjust the speed of said motor, automatic pressure diiferential stabilizing means including a duble-ended cylinder, a double-ended piston reciprocably mounted in said double-ended cylinder, discharge and intake pressure sensing systems adapted to contain a captive fluid and including a pair of bellows positioned to 22 sense said intake and discharge pressures respectively and conduit means connected to said bellows to transmit said captive fluid under the pressures sensed by said bellows, said conduit means being connected to transmit said captive fluid under said intake and discharge pressures respectively to opposed ends of said double-ended cylinder to bias said double-ended piston in proportion to the differential between said intake and discharge pressures, diiferential compensating spring means connected to bias said double-ended piston in a direction opposite to the biasing force exerted by said pressure difierential for maintaining said double-ended piston in equilibrium at a position between the opposed ends of said double-ended cylinder at a selected value of said pressure difierential, said difi'erential piston being reciprocated from said equilibrium position toward either end of said double-ended cylinder in response to increases and decreases respectively in said pressure differential from said selected value, pivot means pivotally connecting said double-ended piston to said actuating lever, a fulcrum positioned to engage said actuating lever when said double-ended piston is in any one of a range of equilibrium positions for causing pivotal movement of said actuating lever about said fulcrum in the direction to decelerate said motor when said double-ended piston is reciprocated from an equilibrium position in said range in response to an increase in said pressure dilierential, said differential compensating spring means being connected to pivot said actuating lever about said pivot means and about said fulcrum in the direction to accelerate said motor when said double-ended piston is reciprocated from an equilibrium position in said range by a decrease in said pressure differential, screw means for adjusting the biasing force exerted on said double-ended piston by said differential compensating spring means to select said selected pressure differential value, automatic emergency speed reduction means including an emergency cylinder, an emergency piston reciprocably mounted in said emergency cylinder, means arranged to pivot said actuating lever about said pivot means and about said fulcrum in the direction to decelerate said motor sufficiently far to open said toggle linkage completely for reducing the speed of said motor to a minimal level in response to reciprocation of said emergency piston, emer gency holder means including a magnetic material mounted on said toggle and a magnet positioned to cooperate therewith for snapping said toggle linkage into a substantially open overcenter position and for releasably holding said toggle linkage in said overcenter position for maintaining the speed of said motor substantially at said minimal level in response to complete opening of said toggle linkage, a discharge pressure valve cylinder, an intake pressure valve guideway, said conduit means being connected to deliver said captive fluid from said discharge pressure sensing system along alternative routes through said discharge pressure valve cylinder to said emergency cylinder and through said intake pressure valve guideway to said emergency cylinder to reciprocate said emergency piston, a discharge pressure valve piston reciprocably mounted in said discharge pressure valve cylinder arranged to block passage of said captive fluid through said discharge pressure valve cylinder and formed with a dis charge pressure valve passage for conducting said captive fluid through said discharge pressure valve cylinder, sealing means positioned to seal off said discharge pressure valve passage When said discharge pressure valve piston is in sealing relationship therewith, said discharge pressure valve piston being arranged to be urged out of sealing relationship with said sealing means in response to the discharge pressure exerted thereon by said captive fluid, discharge pressure valve spring means arranged to bias said discharge pressure valve piston into sealing relationship with said sealing means with suflicient force to allow movement of said discharge pressure valve piston out of sealing relationship with said sealing means only when said discharge pressure exceeds a selected maximum, screw means for adjusting the biasing force of said discharge pressure valve spring means to select said selected maximum, an intake pressure valve cylinder, an intake pressure valve piston reciprocably mounted in said intake pressure valve cylinder, an intake pressure valve plunger movably mounted in said intake pressure valve guideway normally arranged in a blocking position to prevent passage of said captive fluid therethrough and shaped to define an intake pressure valve passage located to conduct said captive fluid through said intake pressure valve guideway when said intake pressure valve plunger is moved from said blocking position to a conducting position, said intake pressure valve piston being connected to urge said intake pressure valve plunger toward said blocking position, said conduit means being connected to deliver said captive fluid from said intake pressure sensing system to said intake pressure valve cylinder for urging said intake pressure valve piston in a direction to maintain said intake pressure valve plunger in said blocking position, intake pressure valve spring means arranged to bias said intake pressure valve plunger toward said conducting position with a force sufliciently weak to move said intake pressure valve plunger into said conducting position only when said intake pressure falls below a selected minimum, and screw means for adjusting the biasing force of said intake pressure valve spring means to select said selected minimum.

9. For use with a motor having a speed control and connected to drive a pump receiving a pumping fluid at an intake pressure and discharging said pumping fluid at a discharge pressure higher than said intake pressure, a pressure governor comprising an actuating lever, connecting means engaging said speed control and arranged to adjust the speed of said motor in response to pivotal movement of said actuating lever, a toggle linkage connected to said actuating lever to close upon acceleration and open upon deceleration of said motor, a warm-up holder for releasably holding said toggle linkage closed for maintaining the speed of said motor at a warm-up level, a handle on said toggle linkage for manually opening and closing said toggle linkage to adjust the speed of said motor, automatic pressure differential stabilizing means including a double-ended cylinder, a double-ended piston reciprocably mounted in said double-ended cylinder, discharge and intake pressure sensing systems adapted to contain a captive fluid and including a pair of bellows positioned to sense said intake and discharge pressures respectively and conduit means connected to said bellows to transmit said captive fiuid under the pressures sensed by said bellows, said conduit means being connected to transmit said captive fluid under said intake and discharge pressures respectively to opposed ends of said double-ended cylinder to bias said double-ended piston in proportion to the differential between said intake and discharge pressures, differential compensating spring means connected to bias said double-ended piston in a direction opposite to the biasing force exerted by said pressure differential for maintaining said double-ended piston in equilibrium at a position between the opposed ends of said double-ended cylinder at a selected value of said pressure differential, said diflerential piston being reciprocated from said equilibrium position toward either end of said double-ended cylinder in response to increases and decreases respectively in said pressure differential from said selected value, pivot means pivotally connecting said double-ended piston to said actuating lever, a fulcrum positioned to engage said actuating 'lever when said double-ended piston is in any one of a range of equilibrium positions for causing pivotal movement of said actuating lever about said fulcrum in the direction to decelerate said motor when said double-ended piston is reciprocated from an equilibrium position in said range in response to an increase in said pressure difierential, said differential compensating spring means being connected to pivot said actuating lever about said pivot means and about said fulcrum in the direction to accelerate said motor when said double-ended piston is reciprocated from an equilibrium position in said range by a decrease in said pressure diflerential, screw means for adjusting the biasing force exerted on said doubleended piston by said differential compensating spring means to select said selected pressure differential value, automatic emergency speed reduction means including an emergency cylinder, an emergency piston reciprocably mounted in said emergency cylinder, means arranged to pivot said actuating lever about said pivot means and about said fulcrum in the direction to decelerate said motor sufficiently far to open said toggle linkage completely for reducing the speed of said motor to a minimal level in response to reciprocation of said emergency piston, emergency holder means including a magnetic material mounted on said toggle and a magnet positioned to cooperate therewith for snapping said togglelinkage into a substantially open over-center position and for releasably holding said toggle linkage in said overcenter position for maintaining the speed of said motor substantially at said minimal level in response to complete opening of said toggle linkage, a discharge pressure valve cylinder, an intake pressure valve guideway, said conduit means being connected to deliver said captive fluid from said discharge pressure sensing system along alternative routes through said discharge pressure valve cylinder to said emergency cylinder and through said intake pressure valve guideway to said emergency cylinder to reciprocate said emergency piston, a discharge pressure valve piston reciprocably mounted in said discharge pressure valve cylinder arranged to block passage of said captive fluid through said discharge pressure valve cylinder and formed with a discharge pressure valve passage for conducting said captive fluid through said discharge pressure valve cylinder, sealing means positioned to seal off said discharge pressure valve passage when said discharge pressure valve piston is in sealing relationshlp therewith, said discharge pressure valve piston being arranged to be urged out of sealing relationship with said sealing means in response to the discharge pressure exerted thereon by said captive fluid, discharge pressure valve spring means arranged to bias said discharge pressure valve piston into sealing relationship with said seal ing means with sufficient force to allow movement of said discharge pressure valve piston out of sealing relationship with said sealing means only when said discharge pressure exceeds a selected maximum, screw means for adjusting the biasing force of said discharge pressure valve spring means to select said selected maximum, an intake pressure valve cylinder, an intake pressure valve piston reciprocably mounted in said intake pressure valve cylinder, an intake pressure valve plunger movably mounted in said intake pressure valve guideway normally arranged in a blocking position to prevent passage of said captive fluid therethrough and shaped to define an intake pressure valve passage located to conduct said captive fluid through said intake pressure valve guideway when said intake pressure valve plunger is moved from said blocking position to a conducting position, said intake pressure valve piston being connected to urge said intake pressure valve plunger toward said blocking position, said conduit means being connected to deliver said captive fluid from said intake pressure sensing system to said intake pressure valve cylinder for urging said intake pressure valve piston in a direction to maintain said intake pressure valve plunger in said blocking position, intake pressure valve spring means arranged to bias said intake pressure valve plunger toward said conducting position with a force sufficiently weak to move said intake pressure valve plunger into said conducting position only when said intake pressure falls below a selected minimum, and screw means for adjusting the biasing force of said intake pressure valve spring means to select said selected minimum.

10. For use with a motor having a speed control and connected to drive a pump receiving a fluid at an intake pressure and discharging said fluid at a discharge pressure higher than said intake pressure, a pressure governor comprising automatic pressure differential stabilizing means, automatic emergency speed reduction means, means connecting said pressure differential stabilizing means to sense the differential between said intake pressure and said discharge pressure and connecting said emergency speed reduction means to sense said discharge pressure and said intake pressure, and means connecting said pressure differential stabilizing means and said emergency speed reduction means for operating said speed control, said pressure differential stabilizing means being operable in response to variation of said pressure differential from a selected value thereof to adjust the speed of said motor in the direction to restore said selected value, said emergency speed reduction means being operable in response to rising of said discharge pressure above a selected maximum and in response to falling of said intake pressure below a selected minimum to reduce the speed of said motor to a minimal level, and magnetic means associated with said means for operating said speed control to magnetically maintain said speed control at a position whereby the speed of said motor is at a minimum level.

11. A pressure governor for use with a motor having a speed control and connected to drive a pump receiving a fluid at an intake pressure and discharging said fluid at a discharge pressure higher than said intake pressure, said pressure governor comprising automatic pressure differential stabilizing means including a piston, automatic emergency speed reduction means, means connecting said pressure differential stabilizing means to sense the differential between said intake pressure and said discharge pressure and connecting said emergency speed reduction means to sense said discharge pressure and said intake pressure, lever means connecting said pressure differential stabilizing means and said emergency speed reduction means to operate said speed control, said lever means including a lever pivoted to said piston and a toggle linkage pivoted to said lever and said speed control, said pressure differential stabilizing means being operable in response to variation of said pressure differential from a selected value thereof to adjust the speed of said motor in the direction to restore said selected value, said emergency speed reduction means being operable in response to rising of said discharge pressure above a selected maximum and in response to falling of said 26 intake pressure below a selected minimum to reduce the speed of said motor to a minimal level, means for adjusting the response of said pressure differential stabilizing means to select said selected pressure differential value, and means for adjusting the response of said emergency speed reduction means to select said selected maximum and said selected minimum.

12. A pressure governor for use with a motor having a speed control and connected to drive a pump receiving a fluid at an intake pressure and discharging said fluid at a discharge pressure higher than said intake pressure, said pressure governor comprising automatic pressure differential stabilizing means including a piston, automatic emergency speed reduction means, means connecting said pressure differential stabilizing means to sense the differential between said intake pressure and said dicharge pressure and connecting said emergency speed reduction means to sense said discharge pressure and said intake pressure, lever means connecting said pressure differential stabilizing means, said emergency speed reduction means to operate said speed control, said lever means including a lever pivoted to said piston and a toggle linkage pivoted to said lever and said speed control, said pressure differential stabilizing means being operable in response to variation of said pressure differential from a selected value thereof to adjust the speed of said motor in the direction to restore said selected Value, said emergency speed reduction means being operable in response to rising of said discharge pressure above a selected maximum and in response to falling of said intake pressure below a selected minimum to reduce the speed of said motor to a minimal level, means for adjusting the response of said pressure differential stabilizing means to select said selected pressure differential value, and means for adjusting the response of said emergency speed reduction means to select said selected maximum and said selected minimum, and magnetic means adjacent said lever means and engageable with said toggle linkage to magnetically hold said toggle linkage to maintain said speed control at a position whereby the speed of said motor is at a minimum level.

References Cited in the file of this patent UNITED STATES PATENTS 1,415,647 Huff May 9, 1922 2,373,143 Samiran Apr. 10, 1945 2,667,150 Coal Jan. 26, 1954 2,764,868 Watson et a1 Oct. 2, 1956 2,771,843 Brown Nov. 27, 1956 2,852,031 Schellers Sept. 16, 1958 

